This invention relates to a mass meter of the type of a conventional weighing scale having a cantilever mechanism provided with a weighing cradle and an electromechanical transducer for sensing a strain of the cantilever to produce a weight indicative signal for measuring the mass of an article on the weighing cradle from which the effect of gravity has been removed.
An example of such type of weighing scale is disclosed in the opened British patent specification No. 2128329A (which is incorporated herein by reference) having the same named inventor. This weighing scale includes two elastic cantilever beam members having different bending rigidity and being arranged in parallel in a vertical plane, a weighing cradle fixed to one of the elastic beam members having greater bending rigidity, a metal wire stretched between the free ends of both elastic beam members. An electromechanoelectric transducer for converting mechanical vibration of the metal wire into an electric oscillation having the same frequency, and means for measuring the frequency and calculating therefrom weight of an article on the weighing cradle. As well known in the art, such a weighing scale measures a force applied to the article by the gravity, that is, the product of mass of the article and acceleration of gravity. Therefore, in using such type of weighing scale to measure the mass, the mass must be calculated from the measured weight and the acceleration of gravity at the place of measurement.
The opened Japanese patent specification No. 52-149154 discloses a weighing scale which uses a reference weight to be both loaded and unloaded for compensating for deviation of the zero-point caused, for example, by variation of the acceleration of gravity. However, the weighing scale disclosed in that specification measures the weight of the article but cannot provide its mass.